Specific heat calculations of III-N bulk materials

We have carried out calculations of the specific heat of the cubic and hexagonal phases of BN, AIN, GaN and InN by employing lattice dynamical results from an adiabatic bond charge model. While each phonon polarization branch contributes equally at high temperatures, it is found that the transverse acoustic branches contribute more at low temperatures. These results, which compare well with available experimental measurements, are used to test the applicability of the routinely employed Debye model based on an isotropic continuum dispersion scheme. The specific heat of the hexagonal phase is predicted to be higher than of the cubic phase at quite low temperatures. A trend in the variation of the specific heat across the sequence BN AIN - GaN - InN has been established in terms of their molar masses. (c) 2006 WILEYNCH Vertag GmbH & Co. KGaA, Weinheim.